1. Shoot it - make sure there are no functioning issues (feeding, extracting, ejecting, etc) and reasonably accurate (in the sense that it's not throwing shots way left or right, which indicates an under- or over-timed barrel). Check the barrel - there are some real sewer-pipes out there, typically South African/Rhodesian - carried a lot and shot a lot. South American Imbels are typically decent - carried a lot and shot little.

2. 922r compliance parts - there should be 7 specific US-made parts if there's a muzzle-device, 6 if it's a plain barrel. If there are none, you'll have to buy them to be legal (usually around $100 will do it, though).

3. Check if it's Metric or Inch pattern - it's much simpler and cheaper to find spare magazines for metric-pattern rifles (metric mags have a small dimple at the front face of the mag, inch mags have a big thick lug).

4. Receiver - the best (upper) receivers are DSA, Imbel and DCI; going downhill from there are Century, Entreprise and Hesse/Vulcan. As long as it works reliably, though, it's not a huge issue apart from future resale value.

5. Headspacing: Have the headspacing checked by someone qualified to do so, although (once you've done a bit of reading) you can do this yourself with a series of 7.62x51mm headspace gauges - Go, No-Go and Field.

Unfortunately, I've never been able to shoot a gun prior to purchasing it. I have always shot similar guns, but I don't know how I could shoot one before buying it, as it would be from a store, gun show, or internet gun auction site.

I agree with everything AndyC said. However, if you don't know what you are looking at and don't know how to fix it yourself (or know a good gunsmith who could do those things for you), I'd order one from DSA. They make a good rifle and they will give you a warranty.

If you get a DSA or Imbel receiver on the rifle AND the rifle has not been build by someone who "modified the receiver to make it work" (which should never be the case, but....) You will have a solid "base" to work from if you have to make repairs to the rifle to get it to function. The other receivers either are low in quality or resale value, thus more difficult to get your $$ back if you try to sell (to fund your M1a).

922 compliance parts are key as well. If the seller can not identify the required US parts, I would either steer clear or plan on bringing the parts count up the next day.

If you have questions about what parts need to be US or how to identify them, either spend some time at FALFILES searching or I would be happy to reply to a PM (normal legal disclaimers invoked of course).

ensure the barrel is in good shape, no pits in the inside, no knicks on the crown. Seems to be mounted straight and gas block aligned with the gas piston (tough to eye ball, but if it is well off, steer clear)

Throat errosion and head space gauges would be very handy as well.

Some quick thoughts:
you can get all the US parts you will need for @150
Barrels can be found for @150, @250 new DSA, sometimes you can get deals
It will cost @50-75 for a barrel change and headspace by a good smith
US Hammer/tigger/sear combo will run you @55-80, depending on brand
Complete new Spring set will cost @30, little less
Complete parts kit for rifle for @150-180
Most orignal, foreign parts are rather inexpensive, however, you can not just use them to replace parts, as you might drop short of your require US parts count.

The typical US parts used to make the rifle legal:
Hammer
Trigger
Sear
Pistol grip
Forearm grip
Butt stock
Gas Piston
Charging handle
Muzzle device
Upper receiver (Only if a DSA, Imbel is foreign, the others I would not bother with)

The mag body, floor plate and follower all count, but I only know of US made floor plates. But if you go this route, the rifle becomes a felony as soon as you put an all foreign mag in it, so beware.

Or order a DSA, if you can get an Stg 58 kit gun from DSA you will be very happy with it.

I appreaciate your responses. I took a look at DSA and I'm impressed. Pricey, but no more than the M1a's out there from Springfield Armory. I think if I get one I'll go new. After all, I'll never sell it (have never parted with any of my guns), so I want it built to be perfect and last a lifetime (or three...grandkids).

You could also PM Grayrider (John) here - he's DSA's rep and could answer any specific questions you might have on their rifles (might even offer you dealer-price - if your FFL is happy to do it just for transfer-costs - if you're nice)

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